The inventive subject matter relates to power supply systems and methods and, more particularly, to uninterruptible power supply (UPS) systems and methods.
UPS systems are commonly used in installations such as data centers, medical centers and industrial facilities. UPS systems may be used in such installations to provide backup power to maintain operation in event of failure of the primary utility supply. These UPS systems common have an “on-line” configuration including a rectifier and inverter coupled by a DC link that is also coupled to an auxiliary power source, such as a battery, fuel cell or other energy storage device. In some UPS applications, a variably available renewable source, such as a photovoltaic source, may be coupled to the DC link of an on-line UPS to provide supplemental power, as described, for example, in U.S. Pat. No. 7,411,308 to Parmley and an article entitled “Photovoltaic UPS” by Jayasimha et al., IEEE TENCON 2003 Conference on Convergent Technologies for Asia-Pacific Region, vol. 4, pp. 1419-1423 (2003).
A frequent goal in such applications is to provide uninterruptible power with high efficiency. Towards this end, on-line UPSs that are used in such applications may support an “efficiency” mode in which the rectifier/inverter conversion chain is bypassed using a static switch when the utility source is within nominally acceptable bounds.